Shear Thinning and Tumbling Dynamics of Single Polymers in the Flow-Gradient Plane

Citations Over TimeTop 10% of 2004 papers

Abstract

The conformational changes imparted on single, flexible DNA polymers by a steady, simple shear flow were directly visualized in the flow-gradient plane. Two fluorescently stained DNA double-strand sizes of 22 μm and 80 μm in contour length were employed, and Wi values of up to 584 were probed (Wi = shear rate × longest polymer relaxation time). By exploitation of the linear proportionality between polymer density and its recorded image, the accessible radius of gyration tensor elements (Gij) were measured. Of those, the ensemble-averaged 〈G22〉 and 〈G12〉 were related to the bulk shear viscosity and first normal stress coefficient, respectively, via the Giesekus stress tensor. We found their respective behaviors to follow power-law decays of Wi -0.52 and Wi -1.28 at large Wi. Polymer dynamics were also investigated. Like rigid ellipsoids of revolution, polymers displayed a constant partition between positive and negative orientations irrespective of shear rate at Wi ≫ 1. Unlike them, however, polymers preferred positive orientations, spending there ∼ 75% or their time vs 50% for rigid ellipsoids. End-over-end tumbling was observed, confirming a long-standing prediction and numerous single-chain computer simulation studies. The tumbling frequency followed Wi0.62, and an equation was derived from simple advection and diffusion arguments to reproduce these observations.

Related Papers

• → Effect of mechanical interactions on the development of shape preferred orientations: a two-dimensional experimental approach(1992)175 cited
• → Lattice Boltzmann simulations of three-dimensional single droplet deformation and breakup under simple shear flow(1999)69 cited
• → Pattern method for higher harmonics from macromolecular orientation in oscillatory shear flow(2020)9 cited
• → Orientational Distributions of a Ferromagnetic Spherocylinder Particle in a Simple Shear Flow. Analysis for a Magnetic Field Parallel to a Shear Flow Direction.(2001)3 cited
• → Rheology of filled polymers. Steady-state shear flow and periodic deformation. 3. Normal stresses and hyperelasticity under simple shear flow(1978)2 cited